In the standard XMPP protocol, a client must ask the server for the user’s contact list (roster)
each time it logs in. If (like certain people) you have a lot of contacts, then it could be a significant saving
in bandwidth and processing time to be able to skip this roster download.

Thankfully that is exactly what roster versioning allows. If your server sees that your client already has an up to date
version, it will simply let it know that, or send a small list of changes if there have been any. This saving is especially useful
on low-bandwidth or pay-as-you-go data connections.

To the best of our knowledge Prosody is currently the only server to support roster versioning, and Gajim
the only client. It would be great to see other clients and servers now follow the lead the two have taken in proving protocol, and improve
login times for all Jabber/XMPP users.

If you want to try out the feature then you’ll want to grab a hold of the latest version of Prosody
(or today’s RC) and Gajim’s trunk code
(which will be released as Gajim 0.13).

About

Prosody is a lightweight and flexible XMPP server designed with ease-of-use and extensibility in mind.